Drying furnace and drying method

Abstract

A drying furnace ( 20 ) for drying an object ( 11 ) by hot air is provided with a heater ( 36, 38, 43, 45 ) that applies radiant heat to a hard-heating region ( 35, 42 ) having a larger heat capacity than the other region ( 37, 44 ) in the object ( 11 ) so as to heat the hard-heating region ( 35, 42 ) to a temperature approximate to a temperature of the other region ( 37, 44 ).

The invention claimed is: 
     
       1. A drying furnace in which an object subjected to a painting operation before being introduced into the drying furnace is dried by hot air, the drying furnace comprising:
 a heater that applies radiant heat to a hard-heating region having a larger heat capacity than another region in the object so as to heat the hard-heating region to a temperature approximate to a temperature of the other region, 
 wherein the heater applies the radiant heat at a timing when the temperature of the hard-heating region measured by a first temperature measuring part reaches a cross-linking temperature of a paint applied onto the object during the painting operation. 
 
     
     
       2. The drying furnace according to  claim 1 , wherein the heater comprises a near-infrared lamp. 
     
     
       3. The drying furnace according to  claim 1 , further comprising:
 a first temperature measuring part that measures the temperature of the hard-heating region and a second temperature measuring part that measures the temperature of the other regions, the first temperature measuring part and the second temperature measuring part being provided on an upstream side of the heater; and 
 a control part that controls a power of the heater based on temperature information from the first temperature measuring part and the second temperature measuring part. 
 
     
     
       4. A drying method for drying an object by hot air using a drying furnace, the drying method comprising:
 a temperature increasing process of increasing a temperature of the object; 
 a temperature measuring process of measuring a temperature of a hard-heating region having a larger heat capacity than another region in the object by a first temperature measuring part and measuring a temperature of the other region by a second temperature measuring part; 
 a local heating process of locally heating the hard-heating region to a temperature approximate to the temperature of the other region by applying radiant heat to the hard-heating region of the object; and 
 a temperature maintaining process of constantly maintaining the temperature of the object, 
 wherein the object is subjected to a painting operation before being introduced into the drying furnace, 
 wherein a timing for applying the radiant heat to the hard-heating region of the object in the local heating process is a timing when the temperature of the hard-heating region measured by the first temperature measuring part reaches a cross-linking temperature of a paint applied onto the object, and 
 wherein the local heating by the radiant heat is applied at the timing when the temperature of the hard-heating region reaches the cross-linking temperature so that a temperature rising speed becomes larger. 
 
     
     
       5. The drying method according to  claim 4 ,
 wherein the object is a vehicle body, 
 wherein a heat source of the radiant heat is a near-infrared ray, and 
 wherein a temperature of the object applied on a portion which is not directly irradiated by the near-infrared ray is increased with heat conduction from the vehicle body.